The present invention relates to a restriction structure in a variable displacement compressor.
In a conventional variable displacement compressor as disclosed in, for example, Japanese Unexamined Patent Publication No. 2001-3860, a low-pressure chamber is formed in a front head in order to improve the reliability of a shaft sealing unit arranged between the housing and the rotary shaft. The low-pressure chamber is shut off from a crank chamber by a first seal member. A second seal member which constitutes the shaft sealing unit is retained in the low-pressure chamber. Refrigerant that reaches the compressor from the outlet of an evaporator flows into the low-pressure chamber. Therefore, the suction pressure of the low-pressure chamber alone is applied to the second seal member, thereby reducing the load on the second seal member as compared with a case where the pressure in the crank chamber is applied to the second seal member.
The structure that uses a pair of seal members to define the low-pressure chamber increases the cost.
Accordingly, it is an objective of the present invention to ensure the high reliability of a shaft sealing unit located between the housing and the rotary shaft of a compressor to seal the housing while reducing the cost.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a variable displacement compressor having a housing assembly, a rotary shaft, a swash plate, pistons, seal means, a retaining chamber, a refrigerant passage, and a restricting member is provided. The housing assembly has a suction chamber, a discharge chamber, a control pressure chamber, and a cylinder block having a plurality of cylinder bores. The rotary shaft extends in the control pressure chamber and protrudes outside from the housing assembly. The rotary shaft is rotatably supported by the housing assembly. The swash plate is supported on the rotary shaft in a tiltable manner and rotatable together with the rotary shaft and is placed in the control pressure chamber. Pistons are retained in the cylinder bores and define compression chambers in the cylinder bores, so that as the pistons reciprocate in the respective cylinder bores based on rotation of the swash plate, a refrigerant is drawn into the compression chambers from the suction chamber, the refrigerant is discharged from the compression chambers to the discharge chamber. An inclination angle of the swash plate is changed by adjusting a pressure in the control pressure chamber. The seal means is provided between the housing assembly and the rotary shaft, for sealing inside the housing assembly. The retaining chamber retains the seal means. The retaining chamber is separated from the suction chamber and the control pressure chamber. The refrigerant passage extends from outside the housing assembly to the suction chamber through the retaining chamber. The refrigerant passage supplies the refrigerant to the seal means. The restricting member restricts the refrigerant from the control pressure chamber to the retaining chamber and releases an internal pressure of the control pressure chamber.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.